1. Technical Field of the Invention
The present invention relates to a cellular communications system and, in particular, to a cellular communications system having an intelligent roaming procedure for enabling a mobile station to select a best service provider from a plurality of service providers.
2. Description of Related Art
People that subscribe to a cellular telephone service do so primarily because of the provided mobility advantage. With a cellular telephone subscription, a subscriber is freed from fixed wireline connections, and may move about a home service area covered by a home service provider to make and receive telephone calls on a mobile station. Recently the subscriber has had an increasing number of opportunities to use the mobile station not only in the home service area, but also when traveling within geographic areas where cellular telephone services are provided through other service providers. The subscriber is referred to as a "roamer" when they use service providers other than their home service provider.
To facilitate the provision of cellular telephone service to roamers, cellular service providers enter into billing and other reciprocity service agreements to allow the subscriber to move among and between visited service areas without interrupting their cellular telephone service. The billing rates and other reciprocity agreements usually differ between the home service provider and the other service providers.
Of course, the subscriber would prefer to utilize the service provider that has negotiated the best available rates with their home service provider, provided the home service provider is not presently available for use by the subscriber. To aid in this selection process, the subscriber currently uses a mobile station having an intelligent roaming procedure which attempts to locate the service provider offering the best service and generally the least expensive services to the subscriber.
Unfortunately, the current intelligent roaming procedure may have difficulty in determining the best service provider especially when the mobile station is located on or near an edge of a service area or coverage area of one of the service providers. The coverage areas of multiple service providers may be contiguous to each other when the service operators utilize the same band or frequency, while the coverage areas may overlap one another when service providers utilize different bands. Thus, when the mobile station is located on or near the edge of one of the coverage areas there may be multiple service providers available for use by the subscriber. The current intelligent roaming procedure may have difficulty in selecting the best service provider from the multiple of service providers that are available, because of an assumption made during the current procedure.
Mobile stations utilizing the current intelligent roaming procedure to receive and analyze channels transmitted by service providers assume that all of the channels transmitted in a given band belong to the same service provider. The assumption is problematic, because when the mobile station receives and analyzes one channel it may not continue to analyze other channels transmitted in the same band that are associated with other service providers that offer better rates to the subscriber. Therefore, the assumption made by the current intelligent roaming procedure may prevent the mobile station from selecting the best service provider especially when the mobile station is located on or near the edge of a coverage area.
Moreover, when the mobile station is located on or near the edge of the coverage area associated with their home service provider it is possible using the current intelligent roaming procedure that the mobile station will select one of the other service providers instead of their home service provider, because the other service providers also transmit channels in the same band used by the home service provider.
Accordingly, there is a need for an intelligent roaming method and system for enabling a mobile station to select a best service provider from a plurality of service providers. There is also a requirement to provide an intelligent roaming method and system that does not automatically assume all channels transmitted in a given band are associated with the same service provider. These and other needs are addressed by the intelligent roaming method and system of the present invention.